We have numbers 7218 and 2124. Let's start adding them together.

Step 1: We'll start by adding the digits 8 & 4 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 1 & 2 in column 2 and get 4.

Step 3: We'll start by adding the digits 2 & 1 in column 3 and get 3.

Step 4: We'll start by adding the digits 7 & 2 in column 4 and get 9.

So, 7218 + 2124 = 9342.

